My teacher gave us an assignment that I don't know how or where to start from He never teach us anything properly! Please do help do this program.. Any help would be greatly appreciated..

The thing is, we have to create a Java program that is called "CashTill" where it has three options, 1. Perform a Sale 2. List of Inventory and 3. Quit Program..

1. Perform a Sale; the user should be able to enter item IDs multiple times (even the same ID multiple times), and should be able to indicate that there are no more items to be entered by typing zero (0). The program should calculate the total cost of the purchase, calculate the relevant tax (assume to be 10.0%), and calculate the total cost payable by the customer and then prints a receipt, which should have the items purchased and the amount of each, the subtotal cost of each item, the subtotal cost of all the items, the total tax amount, and the total cost.
On completion of a transaction, the amount in stock of each relevant item should be updated.

2. List of Inventory; this one lists the name, price, and amount in stock for each item in the “store”. The format of the display is for the student to determine, but the price should be displayed in the Philippine currency format (e.g. P250.00), and the amount in stock should be displayed as an integer (i.e. there is no decimal point).

3. Quit Program; ends the program with a goodbye msg "Thank you for Using CashTill" or something